1. Field of Invention
The present invention relates to a preparation method for medical porous tantalum implant material, especially to a porous tantalum used for medical implantation and a method for preparing the same.
2. Description of the Related Art
A medical porous tantalum implant material is important for specific application of treating traumatic osseous tissues, necrotic femoral tissues or the like. Such metal materials are normally porous stainless steel, porous titanium, and so on. As a porous implant material for the treatment of traumatic osseous tissues and necrotic femoral tissues, the porosity thereof should reach to 30-80%, and the pores should be all interconnected and well-distributed or partially interconnected depending on requirement. Thus, the porous implant material can make the growth phase of the osseous tissue uniform and have lower weight to fit the use of medical implantation.
Due to good biocompatibility and mechanical properties of the insoluble tantalum, the porous form thereof is potential in place of the traditional metal biomaterials mentioned above in order to be used as a medical implant material for the application of treating necrotic femoral tissues. Also, due to the harmlessness, non-toxicity, few of side effects, the rapid development of the medicine, and the further knowledge of tantalum as an implant material, the requirement of porous tantalum for medical implantation is getting more urgent than before, and the criterion of the quality of porous tantalum is getting much higher. As a porous tantalum for medical implantation, having a lot of well-distributed interconnecting pores and mechanical properties adaptable to human body are of great importance for being a novel equivalent material of bony tissues.
The medical porous metal implant material are manufactured mainly by powder sintering, like the preparation of general porous metal materials, especially by impregnating an organic foam body with metal powder and then sintering to obtain a porous metal having a foam structure with well-distributed interconnecting pores (also called “foam impregnation”). However, the porous metal materials with well-distributed interconnecting pores usually do not have sufficient mechanical properties because of the problems of the structure itself, as well as the collapse of the metal powder during sintering process. For now, such problems have not been solved according to any know research reports.
There are not many research and reports about the powder sintering process for making porous tantalum, especially few of papers has mentioned about the preparation of porous tantalum for medical implantation. CN Patent Publication No. 200510032174 discloses “Three-dimensional through-hole or part-hole interconnecting porous metal foam and its preparing method”, and CN Patent Publication No. 200710152394 discloses “Porous foam tungsten and preparation method thereof”. Nevertheless, the porous metal is prepared for the applications of filtering materials, or for aerospace and other applications in high temperature environments. Furthermore, the porous metal processed in such application is not porous tantalum.
Regarding porous tantalum, U.S. Pat. No. 5,282,861 discloses “Open cell tantalum structures for cancellous bone implants and cell and tissue receptors”. The porous tantalum is manufactured by commercial tantalum and a supporter such as a carbon skeleton obtained from heat degradation of polyurethane precursors. The carbon skeleton has multiple dodecahedrons with mesh structures inside and wholly distributed pores, and the porosity thereof reaches to 98%. Next, the commercial tantalum is bound to the carbon skeleton to form porous metal microstructure through chemical vapor deposition (CVD) (also called “chemical deposition”). The porous tantalum material obtained by such processes has a tantalum layer having 40-60 μm of thickness, and has about 99 wt % of tantalum and about 1 wt % based on the weight of whole porous tantalum materials. The patent further discloses that the porous tantalum has 50-70 MPa of compressive strength, 2.5-3.5 GPa of elastic modulus, 63 MPa of tensile strength and 15% of the amount of plastic deformation. However, the ductility of the porous tantalum described above is obviously insufficient causing subsequent processing of the porous tantalum, such as cutting the formed material. Similarly, the porous tantalum prepared by such methods mentioned above like foam impregnation has the same problems.